Pressure-insensitive mass flow controller

ABSTRACT

A method of preventing a mass flow controller from participating in crosstalk in an array of mass flow controllers is described. The method includes sensing and providing a signal indicative of a fluid pressure inside of a mass flow controller with a pressure sensor contained within the mass flow controller, determining a response of a control valve to a rapid pressure perturbation at the inlet of the mass flow controller using the signal indicative of the fluid pressure to avoid overcompensation for the rapid pressure perturbation, and adjusting a control valve contained within the mass flow controller downstream of the pressure sensor, based on the determined response, so that the mass flow controller avoids overcompensating for the rapid pressure perturbation. The pressure sensor is positioned such that the pressure sensor is sensitive to rapid pressure perturbations at the inlet of the mass flow controller.

RELATED APPLICATION

This application is a divisional of U.S. Application Ser. No.10/758,968, filed Jan. 16, 2004, which claims the benefit of U.S.Provisional Application No. 60/440,928, filed Jan. 17, 2003. Thecontents of U.S. application Ser. No. 10/758,968 and U.S. ProvisionalApplication No. 60/440,928 are incorporated here by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to process fluid control assemblies, andmore particularly to shut-off valves for process fluid controlassemblies.

BACKGROUND

Almost every process step during semiconductor wafer processing thatadds, alters or removes material on silicon wafers utilizes one or moreprocess fluids. These process fluids range from inert fluids, such ashelium, to toxic and corrosive fluids, such as chlorine. Consequently,semiconductor wafer processing requires sophisticated fluid deliverysystems that can delivery a variety of process fluids in precise amountsto a wafer processing chamber.

In a typical processing assembly, the process fluids are contained inindividual pressurized cylinders that are under the control of afacility system external to the processing equipment. The fluids arethen supplied to the equipment through tubing, and a fluid panelcontrols the flow of fluid from the point of connection to that tubingto the process chamber. The fluid panel is commonly divided intoindividual process fluid control assemblies, each of which is a completeassembly of components (such as valves, filters, fluid purifiers,pressure regulators, and transducers) for one fluid stream.

FIG. 1 shows a process fluid control assembly 101 configuration in atypical prior art fluid panel. The configuration shown is of the typecommonly used for toxic fluids, such as chlorine. The process fluidcontrol assembly comprises a manual diaphragm valve 103 that serves as asafety device by allowing the flow of fluid through the assembly to bemanually turned off for maintenance and service. Fluid pressure iscontrolled by a pressure regulator 105 and a pressure transducer 107. Afilter 109 is provided to remove impurities from the fluid stream. First111 and second 113 pneumatic valves operate to allow the flow of fluidto be remotely turned on and off by sending an electronic signal to bothpneumatic valves and to the mass flow controller (MFC) 115, the latterof which provides precision control of fluid flow through the processfluid control assembly. Third 117 and fourth 119 pneumatic valves areprovided so that the mass flow controller can be purged for maintenance.(The third and fourth pneumatic valves are typically not present inprocess fluid control assemblies of this type which are designed for usewith inert fluids.) A communication port 121 is provided on the massflow controller to allow it to be accessed and controlled remotely.

While the process fluid control assembly configuration of FIG. 1 allowsthe fluid panel to provide good control over fluid delivery to the waferprocessing chamber, the number of components in this configurationcauses the fluid panel to be exceedingly bulky and complex. This isespecially so for wafer processing chambers that require severaldifferent process fluids.

There is thus a need in the art for process fluid control assembly andfluid panel configurations that are more compact and/or have fewercomponents, without sacrificing functionality, ease of serviceabilityand modularity of the configuration. These and other needs are met bythe devices and methodologies disclosed herein.

SUMMARY

In one aspect, a device is provided which comprises an actuator and ahandle. The actuator is adapted to move the device, in response to apneumatic signal, from a first state (which may be a closed state) intoa second state (which may be an open state), and the handle is adaptedto move the device from the second state into the first state regardlessof whether a pneumatic signal is present. The device may be, forexample, a fluid control assembly equipped with a valve, wherein thevalve is closed in the first state and is open in the second state, orit may be a pneumatically driven latch, wherein the latch is closed inthe first state and is open in the second state. The handle is typicallymanually driven, as by rotating it about an axis, and the actuator istypically pneumatically driven. The device may comprise a diaphragm anda valve seat, and the actuator may be adapted to move the device, inresponse to a pneumatic signal, from a first state in which thediaphragm is pressed against the valve seat, to a second state in whichthe diaphragm is not pressed against the valve seat. The device mayfurther comprise a valve chamber having a fluid inlet and a fluidoutlet, wherein the diaphragm and the valve seat form a seal between thefluid inlet and the fluid outlet. In such embodiments, the fluid inletand the fluid outlet will typically be in open communication with eachother when the device is in the second state.

In another aspect, a combination manual/pneumatic valve for a processfluid control assembly is provided. The valve comprises (a) a housing,(b) a valve chamber disposed in the housing which has a fluid inlet anda fluid outlet and which may also contain a diaphragm and a valve seat,(c) a pneumatically driven actuator which is adapted to move the valve,in response to a pneumatic signal, from a first state in which the flowof fluid between the fluid inlet and the fluid outlet is stopped, into asecond state in which flow of fluid between the fluid inlet and thefluid outlet is permitted; and (d) a handle adapted to move the valvefrom the second state into the first state, regardless of whether apneumatic signal is present at the actuator. When the valve is in thefirst state, the diaphragm and the valve seat typically form a sealbetween the fluid inlet and the fluid outlet; conversely, when the valveis in the second state, the fluid inlet and the fluid outlet aretypically in open communication with each other. The valve may furthercomprise an expansion chamber having a piston therein which is adaptedto move the diaphragm from a position in which it is pressed against thevalve seat to a different position in response to a signal, as, forexample, by advancing along a longitudinal axis in a first direction,and the expansion chamber may be equipped with an inlet adapted tointroduce pressurized air into the expansion chamber, and an outletadapted to exhaust the expansion chamber. The valve may also comprise aspring adapted to maintain a compressive force on the diaphragm.

The handle of the valve may be equipped with a threaded cylinder thatrotatingly engages a complementarily threaded aperture in the housing,thereby moving the valve into the first state. The handle of the valvemay have a shaft that is equipped with a passageway defined by first andsecond apertures that are in open communication with each other, andwherein the first aperture is in open communication with the expansionchamber. The second aperture may be adjustable, by rotation of thehandle, from a first position in which it is in open communication withthe inlet, to a second position in which it is in open communicationwith the outlet. The valve seat may be an o-ring and may be disposedabout the fluid inlet such that the actuator compresses the diaphragmagainst the o-ring when the valve is in the first state.

In some configurations, the valve is adapted such that a spring holdsthe diaphragm against the valve seat when the valve is in the firststate and the pneumatic chamber and piston counteract the spring toallow the diaphragm to move so that the valve can enter the secondstate. The disconnection of the pneumatic chamber from the inlet and theconnection of the pneumatic chamber to the outlet (accomplished by thesingle act of rotating the handle), places the valve in a closedposition and disables the pneumatic control. Such a configuration mayalso include a mechanical linkage such that the rotation of the handlecauses axial force to be applied to the diaphragm, holding it againstthe seat with a force in addition to that provided by the spring.

In still another aspect, a process fluid control assembly is providedherein which comprises first and second pneumatic valves, a mass flowcontroller, and a combination manual/pneumatic valve, wherein the firstpneumatic valve is upstream from the mass flow controller, wherein thesecond pneumatic valve is downstream from the mass flow controller, andwherein the combination valve is upstream from the first pneumaticvalve.

In yet another aspect, a fluid panel is provided herein which comprisesa substrate, and a plurality of process fluid control assembliesdisposed on said substrate. Each of the plurality of process fluidcontrol assemblies comprises first and second pneumatic valves, a massflow controller, and a combination manual/pneumatic valve. The firstpneumatic valve is upstream from the mass flow controller, the secondpneumatic valve is downstream from the mass flow controller, and thecombination valve is upstream from said first pneumatic valve.

These and other aspects are described in greater detail below.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a prior art process fluid controlassembly.

FIG. 2 is a schematic illustration of a combination valve/manual handle(shown in a manually enabled, pneumatically closed position) inaccordance with the teachings herein.

FIG. 3 is a schematic illustration of a combination valve/manual handle(shown in a manually enabled, pneumatically open position) in accordancewith the teachings herein.

FIG. 4 is a schematic illustration of a combination valve/manual handle(shown in a manually disabled valve with a pneumatic signal to open thevalve being provided, but with the valve closed) in accordance with theteachings herein.

FIG. 5 is a schematic illustration of a stem/handle interface inaccordance with the teachings herein.

FIG. 6 is an illustration of the functionalities combined into a massflow controller made in accordance with the teachings herein.

FIG. 7 is a functional illustration showing the fluid path of aconventional thermal-based mass flow controller.

FIG. 8 is a schematic illustration of the fluid path of a mass flowcontroller made in accordance with the teachings herein.

FIG. 9 is a graph illustrating crosstalk in a conventional fluid panel.

FIG. 10 is a graph illustrating the elimination of crosstalk through theuse of a mass flow controller made in accordance with the teachingsherein.

FIG. 11 is a schematic illustration of a process fluid control assemblyconfiguration made in accordance with the teachings herein.

FIG. 12 is an illustration of a fluid pallet made in accordance with theteachings herein.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

As used herein, the term “fluid” is meant to include both liquids andgases.

It has now been found that the length of process fluid controlassemblies, and hence the size of fluid panels, can be reduced bycombining the functionalities of a manual valve and a pneumatic valve(such as the first pneumatic valve 111 of FIG. 1) into a single valve.The resulting combination manual/pneumatic valve reduces the length ofthe process fluid control assembly and the size of the fluid panelwithout adversely affecting the serviceability of the fluid panel orprocess fluid control assembly and the modularity thereof. It has alsobeen found that further reductions in the length of the process fluidcontrol assembly and the size of the fluid panel can be obtained, againwithout adversely affecting the serviceability of the fluid panel orprocess fluid control assembly and the modularity thereof, by combiningthe functionalities of the pressure regulator, pressure transducer, andfilter of a conventional process fluid control assembly such as thatshown in FIG. 1 into the mass flow controller. These and other aspectsand features of the systems and devices disclosed herein are discussedin greater detail below.

FIGS. 2-4 illustrate one embodiment of a combination manual/pneumaticvalve 11 made in accordance with the teachings herein. The combinationvalve has a housing 13 which is typically cylindrical and which containsa centrally disposed expansion chamber 15 and a centrally disposed valvechamber 17. The expansion chamber and the valve chamber are typicallycoaxially aligned. The valve chamber has a process fluid inlet 19 and aprocess fluid outlet 21 defined therein, and is fitted with a diaphragm23 and a valve seat 25 that cooperate to control the flow of fluid intoand out of the valve chamber. Thus, when the diaphragm is spaced apartfrom the valve seat, the process fluid inlet and process fluid outletare in open communication, and fluid is permitted to flow into and outof the valve chamber. However, when the diaphragm is compressed againstthe valve seat (that is, when the valve is if the “off” position), theprocess fluid inlet and process fluid outlet are isolated from eachother, and the flow of fluid through the valve chamber is terminated.Typically, the valve seat will comprise an elastomeric material that hassufficient compliance to achieve a tight seal when a sufficientcompressive force is applied to it, yet has sufficient resiliency toreturn to its original shape when the compressive force is removed. Thevalve seat will most typically comprise a fluoroelastomer which may becoated with a perfluoropolymer, given the chemical resistance of thelatter to commonly used process fluids such as chlorine.

The expansion chamber 15 of the valve is typically cylindrical and has acoaxially aligned and longitudinally extending shaft 27 disposedtherein. The shaft is connected on one end via a mandrel 28 to anactuator 29 which makes contact with the diaphragm 23, and terminates onthe other end in a handle 31. The shaft is fitted with a spring-loadedpiston 33 which is maintained under a minimum compressive force by meansof a spring 35.

The handle is fitted with a threaded male cylinder 37 that rotationallyengages a complementary threaded female receptacle 39. The handle istypically designed to be operated with an ergonomically reasonableamount of force. Consequently, as the handle is rotated in the(typically clockwise) disabling direction, the shaft 27 is advancedalong the longitudinal axis such that the actuator compresses thediaphragm 23 against the valve seat 25, thereby cutting off the flow offluid between the process fluid inlet 19 and the process fluid outlet 21and manually placing the valve in the disabled position. Conversely,when the handle is rotated in the (typically counterclockwise) enablingdirection, the shaft is withdrawn along the longitudinal axis, and thevalve is returned to a pneumatically controlled state. In this state,and in the absence of a pneumatic signal, the spring 35 continues toforce the piston 33, the shaft 27 coupled directly thereto, and theactuator 29 against the diaphragm 23, thereby maintaining the valve in aclosed position. Hence, the handle provides a mechanism wherebypneumatic control of the valve can be overridden solely for the purposesof disabling the valve (that is, to stop the flow of fluid). Bycontrast, the flow of fluid through the valve is enabled only when thehandle is in a manually enabled position and a pneumatic opening signalis present. This aspect of the combination manual/pneumatic valve issignificant from a safety aspect, since it does not allow manipulationof the valve to override the safety interlock circuits that function bydisabling the pneumatic signal.

The housing 13 is also equipped with an air inlet 41 and an air exhaust43 which can be alternatively brought into open communication with acentral passageway 45 disposed in the shaft 27 by rotation of the handle31. The central passageway is in open communication with the portion ofthe expansion chamber disposed below the piston. When the handle 31 isin a manually enabled position as shown in FIG. 2—that is, when thecentral passageway is in open communication with the air inlet, and whenthere is no air signal (i.e., air pressure sufficient to displace thepiston against the spring is not applied) at the air inlet—thecompressive force exerted by the spring 35 against the piston 33 causesthe actuator to press against the diaphragm, hence maintaining the valvein a closed position.

When the handle 31 is in a manually enabled position as shown in FIG.3—that is, when the central passageway is in open communication with theair inlet 41, and an air signal is present (i.e., sufficient airpressure is applied at the air inlet)—pneumatic pressure is applied tothe spring loaded piston 33, by way of the central passageway 45. Solong as the force exerted by this pneumatic pressure is greater than theexpansive force exerted by the spring 35, the spring will be compressed,the piston will be driven into abutment with a stop surface 47 on theshaft, and the actuator 29 will be withdrawn along its longitudinalaxis. This, in turn, allows the diaphragm 23 to expand and bring thefluid inlet 19 and outlet 21 into open communication with each other,thereby permitting a flow of fluid through the valve chamber.

In valves of the type depicted, the diaphragm is typically driven upwardby at least two forces. The first is that the pressure of the fluid inthe inlet 19 or outlet 21 imposes an upward force on the diaphragm. Thesecond is that the diaphragm's resting shape is usually concavedownwards, so that it flexes unless it is being forced down against thevalve seat 25. With respect to this latter feature, it is to be notedthat, in some embodiments, the actuator 29 is not connected to thepiston 33 by a means that allows the piston 33 to pull the actuator 29.In these embodiments, the upward motion of the piston 33 may simplyallow the actuator 29 to be moved upward by the flexion of thediaphragm.

As shown in FIG. 4, when the handle 31 is in a manually disabledposition—that is, when the handle is manually rotated such that thecentral passageway 45 is in open communication with the air exhaust43—the pressure in the expansion chamber is at ambient pressure even ifa pneumatic signal is present at air inlet 41. Moreover, the advancementof the shaft 27 along the longitudinal axis as the handle 31 is rotatedinto a disabled position drives the actuator 29 against the diaphragm23. Consequently, the valve is disabled by the longitudinal displacementof the shaft that precludes the piston being moved away from thediaphragm by the pneumatic signal.

The combination manual/pneumatic valve 11 may be lockable in thedisabled position using a padlock, a cable, or other available lockingdevices (not shown). Hence, the valve may function as a Lock Out Tag Out(LOTO) device. Moreover, to ensure safety in case of failure in thefluid control components upstream of the manual valve, the valve mayalso be designed to withstand an inlet pressure of at least 3000 PSIA inthe disabled position without allowing fluids to pass through the valvefor 72 hours (irreversible damage to the valve is reasonable in thisunlikely scenario).

It will be appreciated from the above description that the valve can bedisabled manually or closed pneumatically, though manual disablement isindependent of the pneumatic input state. Hence, the valve can be openedpneumatically to allow the flow of fluid, only if it is manually in theenabled position, and the valve can also be disabled manually to stopthe flow of fluid, even if a pneumatic signal to open is present. Thisfeature of the valve is highly advantageous from both an emergencyshut-off and maintenance aspect.

FIG. 5 illustrates the shaft/handle interface 61 of the combinationvalve disclosed herein. This interface would typically be disposedinside the threaded male cylinder 37 in the combination manual/pneumaticvalve depicted in FIGS. 2-4. The interface may be machined onto, orsoldered onto, one end of the shaft 27 in the valve of FIGS. 2-4. Thehandle has a hollow cylindrical underbody which is adapted to mate witha complimentary shaped male member (shaft/handle interface FIG. 5) thatprotrudes from the shaft 27 of the valve of FIGS. 2-4. The interface isalso provided with an aperture 65 which is adapted to receive an Allenscrew or other fastening device for securing a handle to the interface.

The shaft/handle interface 61 of FIG. 5 is advantageous in that it canbe provided on each component of the fluid panel that requires a handle,thus allowing the fluid panel to be readily standardized so that thesame handle can be used to operate each component of the panel. Thisalso allows each component fitted with the interface to be easilyretrofitted and standardized as a LOTO device. The dimensions of thefeatures on the shaft/handle interface 61 of FIG. 5 can vary.

The combination manual/pneumatic valve described above in reference toFIGS. 2-4 has several important safety advantages over many existingvalves. One of these safety advantages relates to the use of thecombination valve to provide Lockout/Tagout (AKA, LOTO, Hazardous EnergyIsolation (HEI)). For example, reduction in fluid panel size could beobtained by placing a conventional lockable, manually-operated valve inthe pneumatic control line to the valves, and this would permit thedisabling of pneumatic control in a manner that would arguably meet theregulatory requirements for Lockout/Tagout devices. However, thisapproach is flawed in that the energy isolation could be subverted byconnecting (deliberately or accidentally) another source of actuatingpressure to the process fluid valve. For example, an accidentalconnection could be the result of an attempt to connect a control lineto a different valve, or from the connection of the manually operatedvalve to a process chemical valve other than the one the person intendedto isolate.

In addition, overriding the pneumatic control signal of a normallydisabled valve leaves the valve in a state in which it relies on thespring force being greater than the force applied to the underside ofthe diaphragm by the fluid to keep the valve disabled. Valves can bemade in accordance with the teachings herein that eliminate these flawsby disconnecting the pneumatic control within the valve assembly(preventing cross connection of control lines) and by providing a rigidmechanical linkage that applies closing force to the diaphragm (reducingthe dependence on spring pressure to overcome the opening force appliedby the gas). Notably, the opening force applied by a fluid of a givenpressure at the valve outlet is approximately an order of magnitudegreater than the opening force applied by a fluid of the same pressureon the fluid inlet. Consequently, the valves which rely on a spring tomaintain closure are subject, when disabled, to reverse flow at muchlower pressure than that at which they are subject to forward flow.

Another safety advantage is that the combination of the manual overrideand pneumatic actuation into a single valve renders moot the competitionfor first (closest to the point of connection to the fluid supply)position between pneumatic and manual valves. The manual valves, asdescribed previously, are used to isolate the downstream fluid panelelements and the process chamber from the fluid supply. The safetyadvantage of placing the manual valve first is that it is thenpositioned to isolate all of the other elements of the fluid panel fromthe supply. This minimizes the chance of accidental release (either fromcomponent failure or human error) by minimizing the number of componentsthat are still connected to the supply.

The pneumatic valves serve a different safety function. They may be usedas the actuating elements of several interlock circuits that, inresponse to various conditions, disconnect the fluid supply from theelements of the fluid panel downstream of them and from the processchamber. Among the sensors in such interlock circuits are fluiddetectors. If the detectors sense a leak and remove the actuating signalfrom a valve, control of the flow through the leak depends on whetherthe leak is upstream or downstream of the valve which is no longer beingactuated. Therefore, it is advantageous in many applications to have thepneumatic valve that is the actuating element for such interlocks as farupstream in the assembly as possible. Consequently, the manual andpneumatic valves “compete” for the first position. As noted above, thecombination valve described herein renders this matter moot, as the samevalve is subject to control by both means.

The combination manual/pneumatic valve described above and illustratedin FIGS. 2-4 enables significant reductions in process fluid controlassembly length and fluid panel size by combining the functionalities ofa pneumatic valve and manual shut-off valve into a single component.However, it has also been found that even further reductions in thelength of the process fluid control assembly and in the size of thefluid panel can be obtained, without adversely affecting theserviceability of the fluid panel or process fluid control assembly andthe modularity thereof, through modifications to the MFC. The resultingMFC is referred to herein as a “Pressure Insensitive MFC” (PIMFC). Asseen in FIG. 6, the PIMFC 71 combines into a single unit thefunctionalities of a pressure regulator 73, pressure transducer 75,filter 77, and MFC 79 as those elements are found in a conventionalprocess fluid control assembly such as that shown in FIG. 1. The PIMFCis described in greater detail below. FIG. 7 is a functionalillustration of a conventional thermal-based MFC 81. The MFC consistsprimarily of a control valve 83 and a thermal flow sensor 85. The use ofan MFC of this type necessitates the use of a pressure regulator toeliminate “crosstalk”, that is, pressure perturbations in the supplyline supplying fluid to a first process fluid control assembly that canoccur when a second process fluid control assembly operating from thesame fluid source is brought online. Crosstalk commonly occurs when thesecond process fluid control assembly is supplying the fluid at asignificantly higher pressure than the first fluid control assembly.Such pressure perturbations cause the MFC controlling the first processfluid control assembly to temporarily register an indicated fluid flowrate that is substantially different (typically much lower) than theactual flow rate.

The effect of crosstalk in a process fluid control assembly controlledby a conventional MFC (and without the aid of a regulator) is shown inthe graph of FIG. 9. This graph was generated on a test station using astimulus MFC to create a pressure perturbation of about 3 psi (20.7MPa). The curve denoted “XDOR6” indicates pressure in the fluid line asa function of time as measured by a pressure transducer. The curvedenoted “indicated flow” is the fluid flow through the process fluidcontrol assembly as indicated by the MFC, while the curve denoted “ROR”is the Rate of Rise flow, a standard measurement of the actual fluidflow in the fluid control assembly.

After the initial perturbation of about 3 psi (20.7 MPa), the pressureperturbation relaxed to a pressure difference of about 2 psi (13.8 MPa).However, during the initial perturbation, the difference in indicatedand actual fluid flow at the MFC was about 3 sccm. This demonstrates thetendency of the MFC, in the absence of a pressure regulator, toovercompensate for the initial pressure drop in the fluid supply at theprocess fluid control assembly inlet by ramping up the actual flow rate.The use of pressure regulators is thus necessitated with conventionalMFCs of this type. The pressure regulator functions by controllingcrosstalk by dampening out the pressure perturbations giving rise tocrosstalk. This, in turn, allows the indicated flow rate to more closelytrack the actual flow rate.

FIG. 8 is a functional illustration of a PIMFC 91 made in accordancewith the teachings herein. The specific details of the components of thePIMFC may vary significantly from one product to another, and have beenomitted for purposes of clarity. However, these components areindividually well understood in the art, and hence one skilled in theart will appreciate various specific implementations from the functionalpresentation of these components here.

As with the conventional MFC illustrated in FIG. 7, the PIMFC alsocontains a control valve 93 and a thermal flow sensor 95. However, thePIMFC additionally contains a pressure sensor 97 and a filter 99. Thepressure sensor is upstream of the flow sensor and can be tied into thecontrol loop operating the control valve. Consequently, the PIMFC canrapidly compensate for any changes in the inlet pressure throughsuitable manipulation of the valve. Since the PIMFC is thus adapted todeal with pressure perturbations in the fluid control assembly, the needfor a separate regulator is eliminated. Moreover, since the filter 99 ina conventional process fluid control assembly exists primarily to filterout from the fluid stream debris created by the pressure regulatorbefore the fluid stream enters the MFC, the need for a stand-alonefilter is also eliminated. Consequently, the filter may be simplifiedand incorporated directly into the PIMFC 91 to protect the sensors andactuators from particulate accumulation generated elsewhere upstream.Also, since the PIMFC already contains a pressure sensor, there is noneed for an external pressure transducer, and the displayfunctionalities associated with the pressure transducer may beincorporated directly into the PIMFC (that is, the PIMFC may be providedwith a display to indicate the pressure already being measured by thepressure sensor).

FIG. 10 illustrates the effectiveness of the PIMFC disclosed herein ineliminating crosstalk in a process fluid control assembly without theuse of an external pressure regulator. As with the conventional MFC thatwas the subject of the graph in FIG. 8, the PIMFC was subjected to aninitial pressure perturbation of about 3 psi (20.7 MPa), after which thepressure perturbation relaxed to a pressure difference of about 2 psi(13.8 MPa). However, unlike the conventional MFC, the PIMFC closelytracked the actual fluid flow rate through the process fluid controlassembly during the entire perturbation. This demonstrates that thePIMFC, unlike a conventional MFC, will not overcompensate for pressureperturbations, and hence does not require the use of a separate pressureregulator.

FIG. 11 illustrates a process fluid control assembly 131 made inaccordance with the teachings herein which is suitable for use withtoxic fluids and which incorporates the combination manual/ pneumaticvalve and PIMFC described above. The process fluid control assemblycomprises a combination manual/pneumatic valve 133 of the typeillustrated in FIGS. 2-4, first 135 and second 137 pneumatic valves, anda PIMFC 139. The first 135 and second 137 pneumatic valves allow theflow of fluid to be remotely turned on and off by sending anelectronically controlled pneumatic signal (pressurized air) to bothpneumatic valves. A communications port 141 is provided on the mass flowcontroller to allow it to be accessed and controlled remotely. Thiscommunications port, which may be adapted to accept wires, opticalcables, and other such communications means, may be situated on varioussurfaces of the mass flow controller and may have variousconfigurations.

In contrast to the conventional process fluid control assembly of FIG.1, which requires a pressure regulator 105, pressure transducer 107, andfilter 109, in the process fluid control assembly 131 of FIG. 11, thepressure regulator has been eliminated and the functionalities of theremaining elements have been combined into the PIMFC 139 as describedabove. Consequently, pneumatic valve 113 of FIG. 1 is no longerrequired, since the aforementioned elements can be isolated for purgingor maintenance in the process fluid control assembly of FIG. 11 via thefirst 135 and second 137 pneumatic valves. Furthermore, pneumatic valve111 of FIG. 1 has been combined into the manual/pneumatic valve 133 inthe process fluid control assembly of FIG. 11, also as described above.Therefore, the process fluid control assembly of FIG. 11 is sufficientlymore compact than the conventional process fluid control assembly ofFIG. 1. This compact design also simplifies pallet design for the fluidpanel and reduces the cost thereof. Moreover, because the process fluidcontrol assembly of FIG. 11 has fewer components than conventionalprocess fluid control assemblies such as that shown in FIG. 1, Mean TimeBefore Failure (MTBF) is higher for the entire system, and thusmaintenance costs are reduced.

The process fluid control assembly 131 of FIG. 11 is adapted for usewith toxic fluids such as chlorine. However, one skilled in the art willappreciate that the principles herein may also be extended to processfluid control assemblies adapted for use with inert fluids. This may beaccomplished, for example, by modifying the process fluid controlassembly of FIG. 11 through the elimination of pneumatic valves 135 and137.

FIG. 12 depicts one non-limiting example of a fluid panel 151 whichincorporates a series of process fluid control assemblies 153 of thetype depicted in FIG. 11. In a typical configuration, some of theprocess fluid control assemblies (typically the first six, going fromleft to right) control toxic, corrosive or flammable fluids, and theremainder of the process fluid control assemblies control the flow ofinert fluids. These two types of process fluid control assemblies arereferred to herein as toxic process fluid control assemblies and inertprocess fluid control assemblies, respectively.

Each of the process fluid control assemblies is supported on a commonpallet 155 and comprises a combination manual/pneumatic valve 157 (ofthe type illustrated in FIGS. 2-4), first 159 and second 161 pneumaticvalves, and a PIMFC 163 equipped with a communication port 165. Thefluid panel further includes a main manifold 167 where various processfluids under the control of individual process fluid control assembliescan be mixed to form a fluid stream. The fluid stream exits the mainmanifold via the main manifold outlet 171, from which it can be directedto a process chamber (not shown) or other end use device.

The main manifold is provided with a fluid inlet 173 and a fluid outlet175 that allow it to be flushed with an inert fluid such as N₂ formaintenance purposes or to clear it of residual toxic fluids. The fluidflow through fluid inlet 173 and fluid outlet 175 may be controlled bypurge valve 177, in addition to one or more of the other valves on themain manifold. A fluid line 179 is provided through which the mainmanifold 167 and a purge manifold 160, the latter of which is disposedunder the set of first pneumatic valves 159, can be brought into opencommunication, thus allowing the PIMFCs 163 to be isolated formaintenance or other purposes.

The main manifold 167 is provided with a first, second and third pair ofvalves that respectively consist of first 181, second 185 and third 189inlet valves and first 183, second 187 and third 191 outlet valves. Thefirst 183 and second 187 outlet valves are pneumatically coupled, withthe first outlet valve operating to control the flow of inert fluidsfrom the inert process fluid control assemblies into the main manifold,and the second outlet valve operating to control the flow of toxicfluids from the toxic process fluid control assemblies into the mainmanifold. Thus, for example, the first six process fluid controlassemblies (from left to right) may be under control of the secondoutlet valve 187, and the next six process fluid control assemblies maybe under control of the first 183 outlet valve. Hence, when the first183 and second 187 outlet valves are both enabled, the fluid streamsfrom any enabled inert process fluid control assemblies will mix withthe fluid streams from any enabled toxic process fluid controlassemblies inside of the main manifold 167 and the resulting mixed fluidstream will exit the main manifold through the main manifold outlet 171.

The fluid panel 151 is further provided with pass-through valves 181 and185. These pass-through valves, which are kept enabled during normaloperation of the fluid panel, cooperate with the first 183 and second187 outlet valves, respectively, to regulate the flow of fluid throughthe pump/purge manifold 186 and to allow for bidirectional pumping andpurging of the fluid panel.

The third outlet valve 191 on the fluid panel regulates the flow offluid through inlet 173 for purging and maintenance of the fluid panel.Similarly, the third inlet valve 189 regulates the flow of fluid intothe pump/purge manifold 186 for purging and maintenance purposes. Thus,for example, if the third inlet valve 189 is disabled and the thirdoutlet valve 191 is enabled, then fluid can be made to flow throughfluid line 179 and subsequently through the purge manifold 160 under theset of first pneumatic valves 159 so that toxic fluids can be purgedfrom the toxic process fluid control assemblies.

The principles disclosed herein have been described primarily withreference to combination manual/pneumatic valves and to the use of suchvalves in process fluid control assemblies. However, it will beappreciated that the manual/pneumatic actuators described herein have anumber of applications that extend beyond process fluid controlassemblies. For example, such actuators could be employed in variouslatching systems, such as those used in industrial and high securitysettings. In such applications, the manual/pneumatic actuators wouldmaintain the latch in a closed position (and therefore maintain a door,hatch or other device under control of the latch in a closed position)unless a pneumatic signal is present. Moreover, even if a pneumaticsignal is present, the manual/pneumatic actuator would allow for manualoverride of the pneumatic signal for safety, security, or maintenancepurposes.

More generally, the principles disclosed herein may be applied todevices in which an energy input is provided to cause the movement ofone or more movable components of the device. Such devices may bemodified in accordance with the teachings herein to effect, as theresult of a single manipulation of a manual control, the disconnectionof the energy input and the engagement of a mechanical means of keepingthe movable component (or components) from moving. Specific,non-limiting examples of such modified devices include valves in whichthe energy input is a control signal that allows a hazardous material toflow, and latches in which the energy input is a control signal whichallows access to a hazardous area. The modified device could also be amanual valve that controls actuation air to a pneumatically powereddevice (e.g., a gate valve), and that includes a mechanism that, in thedisabled state, engages a mechanical lock on the pneumatically powereddevice, precluding movement of one or more pneumatically drivencomponents of the device.

It will also be appreciated that, while the principles disclosed hereinhave been frequently illustrated in reference to pneumatically actuateddevices, these principles are also applicable to devices having variousother energy inputs and actuating signals. Such energy inputs include,but are not limited to, electrical and fluid (e.g., hydraulic) signals.

A combination manual/pneumatic actuator has been described herein. Acombination manual/pneumatic valve has also been described herein thatutilizes such an actuator and that combines the functionalities of amanual valve and a pneumatic valve into a single valve. This combinationvalve allows for reductions in the length of process fluid controlassemblies and of fluid panels incorporating these process fluid controlassemblies, without any loss in functionality, ease of serviceabilityand modularity. Fluid panel configurations that make advantageous use ofthe shortened process fluid control assemblies have also been provided.

All the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps orany method or process so disclosed, may be combined in any combination,except combinations where at least some of the features and/or steps aremutually exclusive. Each feature disclosed in this specification(including any accompanying claims, abstract and drawings) may bereplaced by alternative features serving the same equivalent or similarpurpose, unless expressly stated otherwise. Thus unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features. Moreover, although a specificembodiment is specifically illustrated and described herein, it will beappreciated that modifications and variations of the invention arecovered by the above teachings and within the purview of the appendedclaims without departing from the spirit and intended scope of theinvention.

1. A method of preventing a mass flow controller from participating incrosstalk in an array of mass flow controllers, comprising the steps of:a) sensing and providing a signal indicative of a fluid pressure insideof a mass flow controller with a pressure sensor contained within themass flow controller, wherein the pressure sensor is positioned and theflow path from the inlet to the pressure sensor is configured such thatthe pressure sensor is sensitive to rapid pressure perturbations at theinlet of the mass flow controller; b) determining a response of acontrol valve to a rapid pressure perturbation at the inlet of the massflow controller using the signal indicative of the fluid pressure toavoid overcompensation for the rapid pressure perturbation; and c)adjusting a control valve contained within the mass flow controllerdownstream of the pressure sensor, based on the determined response, sothat the mass flow controller avoids overcompensating for the rapidpressure perturbation.
 2. The method of claim 1, further comprisingproviding a signal indicative of a fluid flow inside of the mass flowcontroller with a flow sensor contained within the mass flow controller,wherein determining a response of a control valve to a rapid pressureperturbation at the inlet of the mass flow controller includes using thesignal indicative of the fluid flow.
 3. The method of claim 1, furthercomprising displaying data based on the signal indicative of the fluidpressure.